This application is based on Application No. 2002-134237, filed in Japan on May 9, 2002, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention generally relates to a magneto-generator for generating electric energy under the action of electromagnetic induction taking place between magnets mounted on a flywheel and an armature winding during rotation of the flywheel.
2. Description of Related Art
For having better understanding of the concept underlying the present invention, description will first be made of a conventional flywheel type magneto-generator by reference to FIGS. 5 and 6 of the accompanying drawings, in which FIG. 5 is a top plan view showing partially in section a rotor of a conventional flywheel type magneto-generator which is disclosed, for example, in Japanese Utility Model Laid-Open Publication No. 121380/1992, and FIG. 6 is a vertical sectional view of the same taken along a line VIxe2x80x94VI shown in FIG. 5 as viewed in the direction indicated by arrows.
Referring to the figures, a rotor of the magneto-generator includes a flywheel 1 implemented in a substantially bowl-like shape (hereinafter also referred to as the bowl-shaped flywheel only for the convenience of description), four magnets 2 mounted on the inner peripheral surface of the flywheel 1 with equidistance therebetween in the circumferential direction, a guard ring 3 of a substantially cylindrical shape which is formed by drawing a sheet metal and closely or tightly fit onto the inner surfaces of the magnets 2 which are disposed substantially in an annular array, a magnet securing resin 4 filled in the space defined between the flywheel 1 and the guard ring 3 at both sides and between the adjacent end portions of the individual magnets 2 for fixedly securing the magnets 2 and the guard ring 3 to the flywheel 1 in a so-called integrated structure, a hub or boss 5 formed in the flywheel 1 at a center portion of a bottom wall la for coupling the flywheel to a rotatable shaft (not shown), and a plurality of fins 4a disposed on the bottom wall la of the flywheel 1 with equidistance along the inner circumferential surface of the guard ring 3 for the purpose of generating air currents (also referred to as airflow or currents of gas or the like) for cooling a generator coil (not shown) disposed internally of the flywheel 1.
In the magneto-generator of the structure described above, the flywheel 1 is caused to rotate upon rotation of the rotatable shaft (not shown) coupled to the boss 5, whereby electric energy or electricity is generated under the action of electromagnetic induction taking place between the magnets 2 and the generator coil (not shown) disposed internally of the flywheel 1.
In accompanying to the rotation of the flywheel 1, the fins 4a disposed on the bottom wall la of the flywheel 1 rotate for agitating a gas (air) existing within the interior space of the flywheel 1, as a result of which the generator coil (not shown) heated due to the core loss is cooled.
In the conventional magneto-generator of the structure described above, the gas or air existing internally of the flywheel 1 can certainly be agitated. However, no ventilation holes (air holes) are formed in the flywheel 1. Besides, no flow can forcibly be brought about in the gas or air existing externally of the flywheel 1. For these reasons, ventilation internal of the flywheel 1 can not sufficiently be effectuated in the conventional magneto-generator.
On the other hand, the armature winding serving as the generator coil undergoes heating in proportion to the square of the generated current value. Thus, when exchange of the heated gas is not adequately effected due to poor ventilation as mentioned above, then the electrical resistance of the winding increases as the temperature thereof rises, which results in lowering of the efficiency of electricity generation, giving rise to a problem.
In the light of the state of the art described above, it is an object of the present invention to provide a magneto-generator in which temperature rise of the armature winding serving as the generator coil can positively be suppressed by realizing effective ventilation internally of the flywheel while generating airflows (air currents) externally of the flywheel with high efficiency to thereby effectively prevent the efficiency of electricity generation from being lowered.
In view of the above and other objects which will become apparent as the description proceeds, there is provided according to a general aspect of the present invention a magneto-generator which includes a flywheel implemented substantially in a bowl-like shape, a plurality of magnets disposed on and along an inner peripheral surface of the flywheel, a generator coil disposed internally of the flywheel in opposition to the magnets for generating electricity under the action of electromagnetic induction taking place between the magnets and the generator coil, and a plurality of resin fins disposed along a peripheral edge of the flywheel at an open end thereof for generating forced gas flows in a peripheral region of the flywheel at the open end upon rotation of the flywheel to thereby cool the generator coil.
In a preferred mode for carrying out the invention, the magneto-generator may further include a magnet-fixing resin filled in a peripheral space surrounding the magnets for fixedly positioning the magnets relative to the flywheel. In that case, the fins can concurrently be filled with the magnet-fixing resin.
By virtue of the structure of the magneto-generator described above, temperature rise of the generator coil can positively be suppressed with high efficiency owing to ventilation internally of the flywheel as well as generation of airflows externally of the flywheel, whereby lowing of the electricity generation efficiency can effectively be suppressed.
Further, the fins can be installed inexpensively without need for any additional step of forming the fins in the process for manufacturing the rotor.
The above and other objects, features and attendant advantages of the present invention will more easily be understood by reading the following description of the preferred embodiments thereof taken, only by way of example, in conjunction with the accompanying drawings.